Surgical drill instrument with motor and locking mechanism to receive an attachment and a cutting burr

ABSTRACT

A surgical apparatus having a locking mechanism that receives a cutting burr and that may include a loading and running position. The locking mechanism may include a motor driven spindle that carries a locking pawl and a detent pawl that lock the cutting burr in place an prevent the cutting burr from inadvertently falling out of the surgical drill instrument when in its load position. A diamond-shaped portion of the cutting burr may be formed in a six-sided diamond configuration and a perpendicular back end surface. The end of the cutting burr may include another diamond-shaped portion formed in a six-sided diamond shape surface that mates with a complementary surface formed in the receiving end of the spindle of the motor/locking mechanism. In an aspect, the attachment of the cutting burr is such that the cutting burr has substantially zero axial movement and runs true in the running condition.

CROSS REFERENCE TO RELATED APPLICATION

This application is a continuation of U.S. application Ser. No.14/456,383, filed Aug. 11, 2014, entitled “SURGICAL DRILL INSTRUMENTWITH MOTOR AND LOCKING MECHANISM TO RECEIVE AN ATTACHMENT AND A CUTTINGBURR,” which is a continuation of U.S. application Ser. No. 13/082,029,filed Apr. 7, 2011, entitled “SURGICAL DRILL INSTRUMENT WITH MOTOR ANDLOCKING MECHANISM TO RECEIVE AN ATTACHMENT AND A CUTTING BURR.” Thedisclosures of which are incorporated herein by referenced in theirentirety. The subject matter described in this application is related tosubject matter disclosed in the following commonly assigned application:U.S. patent application Ser. No. 13/082,016, filed on Apr. 7, 2011,entitled “CUTTING BURR SHANK CONFIGURATION,” which is incorporatedherein by reference in its entirety.

BACKGROUND

Surgical drilling instruments may include two releasably attachedmodular components, e.g., a motor/locking mechanism and an attachment,where the attachment attaches to the end of the locking mechanism. Thesemodular components serve to receive and drive a high speed cutting burrthat fits through the attachment and is engaged by the locking mechanismfor high speed drilling, for example, at 80,000 to 90,000 R.P.M. Themotor/locking mechanism may accept different kinds and sizes of cuttingburrs or bits and different kinds and sizes of attachments.

The attachment of the cutting burr or bit to the motor/locking mechanismof may be difficult to use. For example, to install the cutting burrinto some surgical drills, the operator may need to attach theattachment to the locking mechanism, position a lever on the surgicaldrill, and then insert the cutting burr into the attachment. To removethe cutting burr, the tasks may be reversed by placing the lever into araised position and removing the cutting burr. The process is thenrepeated to insert the next cutting burr. In the above process, anoperator may encounter problems if the lever position is moved from theraise position before the cutting burr is inserted.

Other quick release coupling mechanisms include the use of a posteriorand an anterior Double D collet. The collet housing is mounted in linewith the instrument's housing and is rotatable to two positions.Rotation of the collet housing to first, locking position causes a ballto ride in a helical slot for positioning a closure sleeve to urge thelocking ball into the annular groove formed in the distal end of thecutting burr to lock the cutting burr in place. For removal of thecutting burr the reverse procedure is performed. For example, the collethousing is rotated to a second position causing the closure sleeve tomove away from the ball and allow it to release itself from the annulargroove in the cutting burr and allowing the cutting burr to be remove.To insert another cutting burr, the cutting burr is inserted and thecollet housing is rotated back to the locking position. The cutting burrcannot be inserted if the collet housing is in the locked position.

Thus, quick release coupling mechanisms pose difficulties in their use,especially during operations where a cutting burr may only be useablefor less than 10 minutes, and may have to be changed several timesduring a surgical procedure. As such, the efficiency, ease andtimeliness of the cutting burr changing procedure may affect thesurgical procedure.

SUMMARY

Disclosed herein is surgical apparatus having a locking mechanism thatreceives a cutting burr having diamond-shaped portions formed at aproximal end of the cutting burr. The locking mechanism may include amotor-driven spindle, to which a locking pawl and a detent pawl arepivotally attached. The locking pawl may serve to lock the cutting burrin place and the detent pawl may hold the cutting burr in place whenlocking mechanism is in a loading position, and may serve to reduce thelikelihood of the cutting burr inadvertently falling out of the surgicaldrill instrument.

In some implementations, a proximal diamond-shaped portion of thecutting burr may be formed as a six-sided (e.g., hexagonal) diamondconfiguration and include a perpendicular back end surface. Disposedaxially from the diamond-shaped portion formed in the proximal end ofthe cutting burr is another diamond-shaped portion formed having asix-sided (e.g., hexagonal) diamond shape surface that mates with acomplementary surface of the locking pawl of the locking mechanism. Inan aspect, the attachment of the cutting burr within the lockingmechanism is such that is such that the cutting burr has substantiallyzero axial movement and runs substantially true when the surgical drillis in a running condition. In another aspect, insertion of a cuttingburr having a different design will cause the surgical drillinginstrument to vibrate, thus alerting the user that the wrong orincompatible cutting burr is being used.

According to some implementations, the locking pawl may include anincreased mass portion at an end opposite of an engagement end of thelocking pawl that contacts the axially disposed diamond-shaped portion.During use, a centrifugal force is applied to the mass end causing thelocking pawl to pivot and apply greater pressure on the axially disposeddiamond-shaped portion of the cutting burr, thus providing enhancedlocking thereof within the surgical drilling instrument.

This summary is provided to introduce a selection of concepts in asimplified form that are further described below in the detaileddescription. This summary is not intended to identify key features oressential features of the claimed subject matter, nor is it intended tobe used to limit the scope of the claimed subject matter.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing summary is better understood when read in conjunction withthe appended drawings. For the purposes of illustration, there is shownin the drawings exemplary implementations; however, theseimplementations are not limited to the specific methods andinstrumentalities disclosed. In the drawings:

FIG. 1A is a front view illustrating the surgical drilling instrumentand cutting burr and a perspective and sectional view of the lockinginstrument and the attachment the disclosure;

FIG. 1B is a perspective view partially in section illustrating thesurgical drilling instrument and cutting burr and a perspective andsectional view of the locking instrument and the attachment thedisclosure;

FIG. 2 is a perspective view partly in section illustrating theattachment mechanism for attaching the attachment to the lockingmechanism the disclosure;

FIG. 3 is a fragmentary view in perspective and partly in section of thelocking mechanism illustrating the cutter lock housing (intermediatesleeve), locking actuator (outer sleeve) and outer brake mount (innersleeve) the disclosure;

FIG. 3A is a sectional view illustrating the locking actuator (outersleeve) of the locking mechanism the disclosure depicted in FIG. 3;

FIG. 3B is an end view of the locking actuator depicted FIG. 3A;

FIG. 3C is a perspective view of the outer brake mount (inner sleeve) ofthe locking mechanism the disclosure depicted in FIG. 3;

FIG. 3D is a sectional view of the outer brake mount depicted in FIG.3C;

FIG. 4 is a perspective and exploded view of the drive spindle of thelocking mechanism illustrating the locking and detent pawls, the cuttingburr stop pin and the spindle insert the disclosure;

FIG. 5 is an end view of the cutting burr illustrated in FIG. 7illustrating the outermost diamond-shaped portion;

FIG. 6 is a sectional view taken along lines 6-6 of FIG. 7 illustratingthe innermost diamond-shaped portion;

FIG. 7 is a fragmentary perspective and exploded view illustrating theproximal end of the cutting burr and the locking pawl the disclosure;

FIG. 8 is a sectional view of the locking mechanism illustrating theloading position the disclosure;

FIG. 8A is a fragmentary elevated view partly in section with certaincomponents removed to illustrate the braking and un-braking conditionsprovided to assure braking the spindle and motor during loading andrunning conditions of this inventive surgical drilling instrument; and

FIG. 9 is a sectional view of the locking mechanism the disclosureillustrating the running position.

DETAILED DESCRIPTION

While the description contained in the present disclosure uses certainnames for certain instruments and components, the industry may haveother names for these same items, and as it is understood by thoseskilled in this art and to avoid confusion, the following examples arepresented herein without limitation. The surgical drilling instrumentmay be referred to as the cutter, motor, drill and the like; the cuttingburr may be referred to as fluted ball, diamond ball, twist drill,router and the like; and the attachment may be referred to as angleattachment, minimally invasive attachment, controlled depth attachment,speed reducer and the like. The cutter, as used in this description mayalso refer to the motor and locking mechanism.

Overview of the Surgical Drill Instrument

High speed surgical drills are increasingly being used by surgeons whenperforming delicate bone dissection in areas such as the cervical andlumbar spine. Such surgical drills operate at very high R.P.M., and areable to rotationally drive multiple types of attachments and cuttingburrs. As will be described below, the surgical drill instrument of thepresent disclosure receives a cutting burr having a shank that definestwo diamond-shaped portions. The diamond-shaped portions provide forease of insertion and removal of the cutting burr to and from thesurgical drill. The diamond-shaped portions also provide for axiallocking of the cutting burr and enable the surgical drill to directhigher levels of torque to the cutting burr during surgical procedures.

Referring now to FIGS. 1A and 1B, the surgical drill instrument isgenerally illustrated by reference numeral 10 and comprises electric amotor 12, a locking mechanism 14, an attachment 16, a cutting burr 18and a cutting bit 19. The attachment 16 may include an outer caseportion 33 that fits over the locking mechanism 14 and defines therewitha smooth cylindrical portion and transitional tapering portion of theinstrument that provides a good line-of-sight for the surgeon. Thecutting bit 19 is disposed on the distal end of a shank 20.

As shown, electric cable 35 extends from the motor 12 to deliver powerto the motor 12 either via a commercially available electric outlet orconsole which may include a foot pedal control (not shown), of the typeavailable from the assignee, The Anspach Effort, Inc. of Palm BeachGardens, Fla. The motor 12 may drive a spindle 42, the cutting burr 18,the locking mechanism 14 and the attachment 16. As details of the motor12 and console are known in the art, the description thereof is omitted.The motor may include a control mounted to the motor's housing, such asa control lever, that allows the operator to turn the motor on and offor control the speed thereof. The motor may also be a pneumatic motorand the like. The materials used for the surgical drill instrument,attachment and cutting burr are commercially available materialtypically used for the construction of medical equipment and of the typethat may be suitable to be autoclaved. Features of the surgical drill 10and cutting burr 18 will now be described.

Diamond-Shaped Portions 22 and 24

As shown in FIGS. 1, 5 and 6, the shank 20 may have formed at a proximalend thereof, two diamond-shaped portions, 22 and 24. The shank 20 of thecutting burr 18 may be cylindrically shaped, as shown, or may take othershapes, such as polygonal in cross section, and the like. Thediamond-shaped portion 22 is formed on the innermost of the proximal endof the shank 20 and may be milled into the diamond-shaped configuration.The diamond-shaped portion 22 may include a tapered fore wall 28 havinga taper fairing from an inner diameter of the shank 20 to the outerdiameter of the shank 20.

The diamond-shaped portion 24 may be milled at the outermost of theproximal end of shank 20 and may include diamond-shaped configuration(e.g., a key; see, FIG. 5) and a perpendicular aft wall 26. Thediamond-shaped portion 24 may be keyed to be inserted into a key slot107 of the surgical drill 10. The facets of the diamond-shaped portion24 provide positive engagement surfaces in both clockwise andcounter-clockwise rotational directions with the drive recess. Forexample, some surgical drills provide bi-directional rotation, allowingthe surgeon to selectively reverse rotation for various surgicaltechniques. In conventional designs, there may be rotational playbetween a bit end and a drive recess. However, the symmetrical diamondfacets of the diamond-shaped portion 24 provide substantial drivesurfaces in either direction, and thus a sufficient cross-sectionaldimension to meet strength and reliability requirements needed forhigh-speed, large force surgical applications. In addition, thediamond-shaped portion 24 also provides for a unidirectional backwardcompatibility with older drill instruments 10. While the cutting burr 18is described as having two diamond-shaped portions, it is noted thatother polygon profiles are contemplated by the present disclosure, suchas a parallelogram, an octagon, a star shaped pattern, etc. While thediamond-shaped portions 22 and 24 are described as being“diamond-shaped,” it is noted that such terminology is intended toencompass any six-sided (hexagon) shape having a cross-section with flatedges that meet at a six vertices, curved edges that meet at six points,or some combination of both to form the six sides. The flat and curvededges, and combinations thereof, may be applied to other polygon shapeshaving different numbers of sides.

FIGS. 5 and 6 are sectional views of the diamond-shaped portions 22 and24. The two diamond-shaped portions may be different in size, where thediamond-shaped portion 24 is larger than the diamond-shaped portion 22.The apexes 139 and 146 of the diamond-shaped portions 22 and 24 may fallbelow the outer diameter of the shank 20, and both diamond-shapedportions 22 and 24 may be in axial alignment with each other andoriented in parallel relationship. In some implementations, thediamond-shaped portion 24 and the diamond-shaped portion 22 may be thesame size, or the diamond-shaped portion 22 may be larger than thediamond-shaped portion 24. In the various configurations, the apexes 139and 146 of diamond-shaped portions 24 and 22, respectively, are along asame line and in a same plane as the center line A. Additionally, thedimensions of the diamond-shaped portions 22 and 24 are listed indegrees (°) and inches (″) and are substantially as follows:

The angle of the facets of the six-sided diamond in the diamond-shapedportion 22—a=47°;

The width of the facets of the six-sided diamond in the diamond-shapedportion 22—b=0.046″;

The width of the facets of the six-sided diamond in the diamond-shapedportion 24—c=0.065″;

The width of the shank 16 at the space between diamond-shaped portions22 and 24—d=0.029″;

The length of the diamond-shaped portion 22—e=0.068″; and

The length between the proximal end and the back wall of diamond-shapedportion 22—f=0.149″.

As will be described below, the diamond-shaped portion 22 is provided asan abutment surface for axial locking by a retractable locking pawl 50(FIGS. 4 and 7) of the surgical drill 10, whereas rotational forces maybe incident upon the diamond-shaped portion 24. The position andorientation of the diamond-shaped portion 22 is such that the lockingpawl 50 may lock the cutting burr 18 in the surgical cutting instrumentas the diamond-shaped portion 22 mates with a complementary surfaceformed on the engagement end of the locking pawl 50.

Locking Mechanism 14

Aspects of the locking mechanism 14 are generally illustrated in FIGS.1, 3, 3A, 3B, 3C, 3D, 8, 8A and 9. The locking mechanism 14 receives thecutting burr 18, and may include a motor driven spindle 42 that carriesthe locking pawl 50 and a detent pawl 52. In a loading position of thelocking mechanism 14, an inner sleeve of the locking mechanism 14engages the spindle 42 to brake the motor 12 and spindle 42. The innersleeve engages the locking pawl 50 to hold it in a position thatprevents it from engaging the diamond-shaped portion 22 of the cuttingburr 18. Meanwhile, the detent pawl 52 is biased by a spring 64 suchthat an engagement end of the detent pawl 52 comes into contact with thediamond-shaped portion 22 with sufficient force that will allow thecutting burr 18 to be moved in and out, but yet reduces the likelihoodthat the cutting burr 18 may inadvertently fall out when the surgicalcutting instrument is in the loading position.

With the cutting burr 18 inserted into the locking mechanism 14, thelocking mechanism may be changed from the loading position to therunning position by an outer sleeve that is rotated to force the innersleeve to move axially in a position to disengage the spindle 42 andlocking pawl 50, thus allowing the locking pawl 50 to deploy and engagethe diamond-shaped portion 22 of the cutting burr 18 to lock it intoposition. As noted above, the locking pawl 50 serves to lock the cuttingburr 19 in place by engaging the diamond-shaped portion 22,substantially reducing axial movement. In the running position, thesurgical drill 10 and cutting burr 18 are ready for use in a surgicalprocedure.

The details of the locking mechanism 14 will now be described. FIG. 1Billustrates that the locking mechanism 14 may include a retainer ring 34mounted on the proximate end that threadably engages, via threads 36formed on the outer periphery surface of retainer ring 34, complementarythreads (not shown) formed in the housing of electric motor 12 so as tobe coupled thereto. Spanner engaging apertures 40 may be formed on thesmaller diameter portion of retainer ring 34 to allow a spanner wrenchto secure the locking mechanism 14 to motor 12. The distal end ofattachment 16, when assembled, may encapsulate the locking mechanism 14and defines with the motor, a smooth cylindrical shaped instrument thatis tapered that serves as a handle while providing an excellent line ofview for the surgeon to use in a medical procedure. The lockingmechanism, spindle, attachment and the operation are described below.

As shown in FIG. 3, the locking mechanism 14 may include threeconcentric sleeves, 44, 46 and 48, the spindle 42, the locking pawl 50,the detent pawl 52, a locating dowel pin 54, a coil spring 56, a pair ofdriving balls 58 and 60, and pawl springs 262 and 264. The motor drivenspindle 42 is mounted about axis A for rotary motion. Sleeves 44, 46 and48 are concentrically disposed relative to spindle 42 and all arecoaxially disposed around center line A. The locking pawl 50 and thedetent pawl 52 are pivotally mounted on spindle 42 and rotate therewith.

The three concentric sleeves 44, 46 and 48 may provide severalfunctions, as will be explained below. The outer sleeve 44 may define alock actuator which is fixed relative to the spindle 42, and has a smallcircumferential movement for the purpose of positioning balls 58 and 60to ultimately position inner sleeve 48 linearly. The outer sleeve 44 mayinclude an outer casing portion 61, outwardly projecting flange portion62 extending radially outwardly from the aft end, a pair of projectionsor tabs 64 extending axially from the fore end thereof and diametricallydisposed hemispherical slots 63 and 65. The intermediate sleeve 46 thatdefines the cutter lock housing, is fixed relative to spindle 42 andouter sleeve (lock actuator) 44 and may be formed from a main hollowcylindrical member 66 having a radial outward flange portion 68 disposedon the aft end and an attachment portion 70 disposed on the fore end anda pair of diametrically opposed cam slots 86 and 88 formed intermediatethe ends thereof.

As shown in FIG. 8, a flange portion 62 and a flange portion 68 arespaced from each other defining an annular space 72 providing sufficientspace for sleeve 44 to rotate. The inner sleeve (outer brake) 48 definesa brake, and locking pawl 50 engagement and disengagement member isfixed relative the spindle 42 and is movable rectilinearly. The innersleeve 48 may include a main body portion 78, a tapered end portion 80and spaced O-ring inner and outer retaining flanges 82 and 84 forsupporting O-rings 83 and 85, which serve to seal the motor from foreignmatter and diametrically opposed apertures 77 and 79. A portion of balls58 and 60 fit into apertures 77 and 79, respectively, hemisphericalslots 63, 65, respectively and through cam slots 86 and 88,respectively, and serve to move inner sleeve 48 linearly. When the outersleeve 44 is rotated a portion of balls 58 and 60 bears against it sothat the hemispherical slots in the outer sleeve 44 rotate the capturedballs in a circumferential direction.

A portion of balls 58 and 60 pass through cam slots 86 and 88,respectively, that are contoured to define a particular linear movement,and a portion of balls 58 and 60, extend into apertures 77 and 79,respectively, such that the contour of clam slots 86 and 88 serve tocause the balls to move inner sleeve 48 axially thereby effectuatingbraking and un-braking of the spindle 42 and motor 12 and the engagementand disengagement of the locking pawl 50. This movement may provide abraking function, but it also allows the locking pawl 50 to pass throughthe spindle 42 wall and engage the diamond-shaped portion 22 of cuttingburr 18. A coil spring 56 is disposed between the ball bearing 90 andthe O-ring retaining flange 85 for biasing inner sleeve 48 toward thefore end of locking mechanism. When sleeve 48 is rotated in onedirection, the spring 56 compresses and in the opposite direction coilspring 56 becomes uncompressed.

Spindle 42

The spindle 42 is generally illustrated in FIGS. 4, 8, 8A and 9. Asshown, the locking pawl 50 and detent pawl 52 are pivotally mounted tothe spindle 42 and rotate therewith during operation of the surgicaldrill instrument 10. The locking pawl 50 may include an increased massend 128 such that rotation of the spindle 42 during use applies acentrifugal force to the mass end 128. The increased force on the massend 128 causes the locking pawl 50 to pivot and apply greater pressureon the diamond-shaped portion 22 of the cutting burr 18, thus providingenhanced locking thereof within the surgical drilling instrument 10.

Further, in accordance with some implementations, when the cutting burr18 is inserted into the surgical drilling instrument 10, the spindle 42,the locking pawl 50 and the detent pawl 52 are deployed at apredetermined alignment such that they are rotationally balanced andprovide a substantially vibration-free operation. However, if adifferent (e.g., less compatible) cutting burr is inserted, the spindle42, the locking pawl 50 and the detent pawl 52 may not attain thepredetermined alignment, thus the surgical drilling instrument 10 mayvibrate during use to warn an operator of the potential incompatibility.

The spindle 42 has a drive attachment end 92 at the aft end connected tothe drive shaft (not shown) of the motor 12 and being driven thereby,and an attachment portion 94 at the fore end thereof for attaching tothe attachment 16. Bearings 160 and 162 disposed inside the fixed sleeve46 serve to support spindle 42 for rotary motion. The main body portion96 of spindle 42 is a cylindrical and hollow and may include a reduceddiameter portion 98 formed intermediate the ends thereof, a conicalshaped portion 100 defining a braking surface formed intermediate theends thereof, opposing flattened portions 102, opposing spring retainerrecesses 104 and a plurality of apertures. The spindle 42 may include aninsert 106 that is milled to define a diamond-shaped key slot 107 thatis rigidly supported in the cavity of spindle 42 and a pointed shapedinlet end 109 serves to facilitate the alignment and insertion of thecutting burr 18.

Drilled opposing holes 108 align with drilled opposing holes 110 formedin insert 106 for receiving dowel pin 54 which serves to locate thecutting burr when inserted into the spindle 42 and when the end thereofabuts there against. The opposing drilled holes 112 and 114 formed inthe conical portion of spindle 42 serves to support the axles 116 and118, respectively that pass through the holes 120 and 122 formed in thelocking pawl 50 and detent pawl 52, respectively to provide pivotalsupport.

As best shown in FIGS. 8, 8A and 9 the locking pawl 50 may include thelever arm 124, cutting burr engagement end 126 and an increased mass end128. The spring 262 fits into retainer 104 and bears against theunderside of the increased mass portion of lever 124 and biasesengagement end 126 toward the center line A causing the locking pawl topivot about axle 116 in a counterclockwise direction.

The detent pawl 52 is similarly constructed, but may not include theincreased mass end. The engagement end 129 of detent pawl 52 iscontoured differently from the engagement end 126 of the locking pawl 50and is contoured in a generally hill shape and is sized to partially fitinto the diamond-shaped portion in the cutting burr on the opposite sideof the engagement end 126. The spring 264 biases the lever 152 to rotatein a clockwise direction about axle 118 to place the hill shaped portioninto the diamond-shaped portion with sufficient force that will allowthe cutting burr to be moved in and out when the cutting burr isinserted and removed and yet prevent the cutting burr from inadvertentlyfalling out when the surgical cutting instrument is in the loadingposition. As will be described in more detail hereinbelow, spindle 42may include an enlarged cut out portion 154 that extends through thespindle 42 and allows the locking pawl 50 to engage the cutting burr viadiamond-shaped portion 22 and provides a passageway for detent pawl 52to partially fit into diamond-shaped portion 22 of the cutting burr wheninserted into the central bore 156.

FIG. 7 illustrates the contour on the engagement portion of locking pawl50 and the wing shaped portions 142 and 144 that increase the mass 128at the end of the locking pawl 50. The engagement end 126 may becontoured in a V-shape with inner surfaces 132 and 134 that fit againstthe facets 136 and 137 of the diamond-shaped portion formed in thecutting burr. A back face 130 at the end 140 of the locking pawl 50 mayabut against the inner face 138 at the aft end of the diamond-shapedportion 24 and the configuration of the engagement portion. Owing to thedesign of the engagement end 126 of locking pawl 50 and the proximateend of the cutting burr 18, the cutting burr 18 is prevented fromdisplacing axially when running. In other words, there is substantiallyno axial play in the surgical cutting instrument, which provides forprecision cutting, shaping and the like. In operation, the wings 142 and144 extending from the side walls of locking pawl 50 at the mass end 129add pressure to the engagement end 126 when running because of thecentrifugal force created by the rotation of the spindle 42.

Attachment 16

The attachment 16 is generally illustrated in FIGS. 1 and 2, and mayinclude a main housing 170 having a cut-out grooved upper surface 173that serves as a handle and control for the surgeon or operator forplacing the surgical drilling instrument in the loading and runningpositions. The attachment 16 may include a central bore to allow thecutting burr to pass there through and a disk 174 laterally mounted in acentral cavity 172 of the attachment 16 and is formed with judiciouslyspaced slots 178 and 179 for deploying the surgical instrument in theloading and running position as will be described in detail hereinbelow. The central cavity 172 in main housing 170 is sized to fit overthe sleeve 44 and abut against the retainer ring 34 to define a smoothouter surface of the instruments, saved for the groove portion 173. Disk174 is fixedly secured in central cavity 172 and may include a centralbore 175 and a pair of the back-to-back axial cut outs 176 and 178.

To connect attachment 16 to the locking mechanism 14, the end of lockingmember is inserted into central cavity 172 and any two of the cog gears180 fit through and pass cut out 178 so that the surface 184 at the aftend extends behind the end 186 of hollow disk 174 and fit in the annularspace 190. Also, projections or lugs 64 extending from locking mechanism14 fit into cutout 176, as shown in FIG. 2. The outer surface of sleeve44 snugly fits against the inner surface of ring 174 so as to be held inposition or alternatively, a resilient member like an O-ring 183 can bemounted on the inner surface of the ring 174 adjacent to cut out 178.The above places the locking mechanism 14 surgical drilling instrument10 in the loading position. To change the locking mechanism 14 to therunning position, the attachment 16 is rotated via the main housing 170causing the cog wheel 171 and the cog gear 180 to rotate in the space190 adjacent to the end of the ring 174 and by virtue of the connectionof lugs 64 connected to actuator 16, the locking mechanism will beplaced in the running position.

Thus, with the structure and interoperation of the various components ofthe surgical drilling instrument now described, the operation and use ofthe surgical drilling instrument will now be introduced.

Operation of the Surgical Drilling Instrument 10

During a surgical procedure, a particular attachment 16 and cutting burr18 may be selected by e.g., a surgeon or operator to be used with thecutter. The operator may first attach the attachment 16 to the lockingmechanism 14 by inserting the attachment 16 so that the main housing 170of attachment 16 abuts against and aligns with the retainer ring 34. Thecog wheel 171 and cog gear members 180 will align with cutout 178 andpass therethrough until the aft end fits into the annular space 190.Also the lugs 64 will align with and fit into cutout 176. (See FIG. 2).

The cutting burr 18 is then inserted through the fore end passing thecentral cavity in spindle 42 so that the diamond-shaped portion 24aligns with and fits into the diamond-shaped key slot 107 formed inspindle 42 or insert 106. This constitutes the loading position as shownin FIG. 8. The locking mechanism 14 is held in position in theattachment by virtue of a tight fit or by the aid of the resilient ring177. In the loading position (FIGS. 8 and 8A), sleeve 48 is urged bycoil spring 56 toward the fore end so that the tapered surface 80 bearsagainst the conical surface 100 of spindle 42 serving to lock thespindle 42 and brake the motor and preventing them from rotating. Thesleeve 48 bears against locking pawl 50 and holds it in a disengagementposition so as to prevent it from engaging cutting burr 18.

When the cutting burr 18 is completely inserted, the end thereof willabut against dowel pin 54 establishing the distance the cutting burrprojects beyond the attachment 16. The detent pawl 52 that is pivotallyconnected to spindle 42 is urged by spring 62 to project through thecutout 154 in spindle 42 to partially fit into diamond-shaped portion22. The spring rate of spring 62 is selected to assure that the detentpawl 52 has sufficient force to prevent the cutting burr 18 from fallingout of the cutter inadvertently and yet, permit the removal of thecutting burr without requiring a great deal of force. The surface 129 ofdetent pawl 52 is contoured to facilitate the removal and insertion ofthe cutting burr 18.

To place the cutter in the running position, the main housing 170 ofattachment 16 is rotated causing sleeve 48, in turn, to move axiallytoward the rear end of locking mechanism 14 (FIGS. 9 and 8A). This isoccasioned by positioning balls 58 and 59 as will be immediatelyexplained. As mentioned above, a portion of balls 58 and 60 fit intohemispherical slots 63 and 65 of the outer sleeve 44, extend through camslots 86 and 88 of sleeve 46 and fit into apertures 77 and 79 of sleeve48. Rotation of the outer sleeve 44, say 90 degrees, by virtue ofrotating attachment 16, causes the balls 58 and 60 to travel in camslots 86 and 88 formed in sleeve 46.

The ball portions fitting into apertures 77 and 79 cause the sleeve 48to move axially against the force of spring 56 toward the rear end ofthe locking mechanism 14. As shown in FIGS. 9 and 8A, when sleeve 48moves rearward it unlocks both locking pawl 50 and spindle 42 (see thedash lines in FIG. 8A). This movement of sleeve 48 allows the engagementend 126 of locking pawl 50 to pass through the aperture 154 in spindle42 and engage a portion of the six-sided diamond (top portion as viewedin FIG. 9) and lock cutting burr 18 in place.

In accordance with some implementations, the cutting burr may beinstalled when the locking mechanism 14 is in the loading and runningposition. For example, if during a surgical procedure the originalcutting burr becomes worn out and needs to be replaced, the lockingmechanism 14 may be placed in the loading position to allow the cuttingburr 18 to be removed. As such, the balls 58 and 60 are re-positioned tothe original position allowing spring 56 to force sleeve 48 to movetoward the front of the locking mechanism 14. This locks the spindle 42and retracts the locking pawl 50, as noted above. If the lockingmechanism 14 is positioned from the loading position to the runningposition prior to inserting the replacement cutting burr 18, lockingpawl 50 is returned to the locking position to engage the diamond-shapedportion 22 of the cutting burr.

Notwithstanding this condition, the cutting burr 18 may still beinserted even though the locking mechanism is in the running position.In particular, as the cutting burr 18 is inserted and forced inwardlytoward the key slot 107 in spindle 42, the outer diameter at theproximal end of the cutting burr 18 will abut the contoured end of theengagement end 126 of the locking pawl 50, forcing it upwards againstthe force of spring 62. The spring rate of the spring 62 may be a valuethat will allow the cutting burr 18 to proceed to the dowel pin 54within the key slot 107. As such, as the cutting burr 18 proceeds to thedowel pin 54, the spring 62 will cause the engagement end 126 of thelocking pawl 50 to engage the diamond shape portion 22, thus lockingcutting burr 18 in position. As such, the surgical drilling instrument10 is now ready for use in the medical procedure.

Thus, as described herein, the apparatus of the present disclosureprovides for a locking mechanism and attachment that are relativelysimple to manufacture and that are user friendly. The locking mechanismand attachment provide for relatively easy insertion and removal of thecutting burr. The diamond-shaped portions limit axial play of thecutting burr and provide a substantial surface area for driving thecutting burr with higher torque from surgical drilling instrument motor.

While particular aspects of the present subject matter described hereinhave been shown and described, it will be apparent to those skilled inthe art that, based on the teachings herein, changes and modificationsmay be made without departing from the subject matter described hereinand its broader aspects and, therefore, the appended claims are toencompass within their scope all such changes and modifications as arewithin the true spirit and scope of the subject matter described herein.

What is claimed:
 1. A surgical drill, comprising: a cutting burr; arotatable spindle for driving the cutting burr; a locking mechanismcoupling the cutting burr to the spindle such that rotational movementof the spindle is translated to the cutting burr, the locking mechanismcomprising a plurality of concentrically disposed sleeves concentric tothe spindle, the plurality of sleeves including an outer sleeve, and anintermediate sleeve located between the outer sleeve and the spindle,where the outer sleeve includes a tab extending axially from a distalend of the outer sleeve; an attachment member coupled to the lockingmechanism such that the locking mechanism is received within a centralbody of the attachment member, where rotational movement applied to theattachment member results in a corresponding rotational movement of aportion of the locking mechanism; and a motor for driving rotationalmovement of the spindle, wherein the intermediate sleeve extends throughthe outer sleeve and includes an engagement feature at a distal end ofthe intermediate sleeve for engaging a portion of the attachment member.2. The surgical drill of claim 1, further comprising an inner sleeveconcentrically disposed between the spindle and the intermediate sleeve,the inner sleeve fixedly coupling the cutting burr to the lockingmechanism.
 3. The surgical drill of claim 1, wherein the attachmentmember includes an outer case defining a cylindrical portion and atransitional tapering portion for providing a line-of-sight for anoperator of the surgical drill along the attachment member toward adistal end of the cutting burr, wherein, the cylindrical portion of theouter case defines the central cavity receiving the locking mechanism.4. The surgical drill of claim 1, wherein the attachment member includesan annular-shaped disk mounted within the central cavity of theattachment member, wherein the disk is positioned adjacent a distal endof the locking mechanism within the central cavity.
 5. The surgicaldrill of claim 4, wherein the disk includes an increased diametercylindrical portion and a reduced diameter cylindrical portion, whereinthe increased diameter cylindrical portion is positioned toward aproximal end of the surgical drill and the reduced diameter cylindricalportion is positioned toward a distal end of the surgical drill, whereinthe increased diameter cylindrical portion is adjacent a cylindricalportion of an outer case of the attachment member and the reduceddiameter cylindrical portion is adjacent a transitional tapering portionof the outer case, the transition tapering portion providing aline-of-sight for an operator of the surgical drill along the attachmentmember toward a distal end of the cutting burr.
 6. The surgical drill ofclaim 4, wherein the disk includes a slot extending from a proximal endof the disk toward a distal end of the disk, wherein the tab extendingfrom the distal end of the outer sleeve is received within the slot toreleasably couple the outer sleeve and the disk to fix a rotationalposition of the outer sleeve with respect to the disk, wherein a distalend surface of the outer sleeve abuts a correspondingly shaped proximalend surface of the disk.
 7. The surgical drill of claim 6, wherein diskincludes a cutout extending from a distal end of the disk toward aproximal end of the disk, wherein the engagement feature provided on theintermediate sleeve extends radially at the distal end of theintermediate sleeve, the engagement feature sized and configured toreleasably engage the cutout provided on the disk.
 8. The surgical drillof claim 7, wherein the engagement feature includes a cog wheel andcorresponding cog gear member extending radially from the cog wheel. 9.The surgical drill of claim 7, wherein the locking mechanism is movablebetween a loading position where the cutting burr can be removed fromthe locking mechanism and a running position where the cutting burr isretained within the locking mechanism, wherein in the loading positionthe engagement feature of the intermediate sleeve extends through andbeyond the distal end of the disk.
 10. The surgical drill of claim 9,wherein in the loading position the engagement feature extends throughand beyond the cutout.
 11. The surgical drill of claim 9, whereintransitioning the surgical drill from the loading position to therunning position includes positioning the tab extending from the distalend of the outer sleeve into engagement with the slot in the disk, andpositioning the engagement feature of the intermediate sleeve intoengagement with the cutout of the disk, such that the outer sleeverotates with respect to the intermediate sleeve in response torotational movement applied to the attachment member to engage andretain the cutting burr within the locking mechanism such thatrotational movement of the spindle is translated to the cutting burr.12. The surgical drill of claim 11, wherein rotational movement appliedto the attachment member results in an equivalent rotational movement ofthe outer sleeve.
 13. The surgical drill of claim 4, wherein the lockingmechanism extends through the disk such that the distal end of thelocking mechanism extends beyond a distal end of the disk within thehousing.
 14. The surgical drill of claim 4, further including an o-ringmounted on an inner surface of the disk.
 15. The surgical drill of claim1, wherein the attachment member includes a central bore to allow thecutting burr to pass therethrough.
 16. The surgical drill of claim 1,wherein the locking mechanism is coupled to the motor via externalthreads provided on the locking mechanism sized and configured to matewith a corresponding threaded portion provided on a motor housing.
 17. Amethod of loading a cutting burr in a surgical drill, the surgical drillcomprising a motor, a locking mechanism and a detachable attachmentmember, a cutting burr, and a rotatable spindle for driving the cuttingburr, the locking mechanism movable between a loading position and arunning position, the method comprising: coupling the attachment memberto the locking mechanism such that the locking mechanism is in theloading position; inserting the cutting burr into the surgical drillthrough an end of the attachment member and into the locking mechanism;and placing the surgical drill in the running position by moving theattachment member to cause the locking member to engage and retain thecutting burr and translate rotational movement of the spindle to thecutting burr, wherein the locking mechanism is received within a centralcavity of the attachment member, the locking mechanism including aplurality of concentrically disposed sleeves concentric to the spindle,the plurality of sleeves including an outer sleeve and an intermediatesleeve located between the outer sleeve and the spindle, wherein theintermediate sleeve extends through the outer sleeve and theintermediate sleeve includes an engagement feature at a distal end ofthe intermediate sleeve for engaging an annular disk provided betweenthe locking mechanism and a distal end of the central cavity, wherein inthe loading position the engagement feature of the intermediate sleeveextends beyond the annular disk such that the engagement feature rotatesfreely of the attachment member and the annular disk.
 18. The method ofclaim 17, wherein transitioning the surgical drill from the loadingposition to the running position includes positioning a tab extendingfrom a distal end of the outer sleeve into engagement with a slotprovided in the disk, and positioning the engagement feature of theintermediate sleeve into engagement with a cutout provided in the disk,such that the outer sleeve rotates with respect to the intermediatesleeve in response to rotational movement applied to the attachmentmember to engage and retain the cutting burr within the lockingmechanism such that rotational movement of the spindle is translated tothe cutting burr.